In recent years, development of lighting apparatuses using a solid state light-emitting devices such as LEDs and EL devices has been made progress. In lighting apparatuses of this type, when light-emitting devices are heated by lighting, the output of the light-emitting devices decreases by the heat, and the life of the light-emitting devices is shortened. Therefore, measures to suppress increase in temperature of LEDs are taken for lighting apparatuses using, for example, LEDs as light source.
As measures for heat radiation, known are a method of radiating heat of LEDs from the main body side by attaching a board, on which a plurality of LEDs are mounted, in contact with the apparatus main body made of metal, and a method of radiating heat of LEDs through a heat radiation plate by attaching a board, on which the LEDs are mounted, in contact with the heat radiation plate.
However, when LEDs generate heat, the board on which the LEDs are mounted is also heated and expanded by heat. Therefore, when the board is fixed onto a heat radiation member such as the main body and a heat radiation plate, the board may be distorted by thermal stress. Conversely, when the board is not fixed onto the heat radiation member in a state where the whole surface of the board is brought into close contact with the heat radiation member, the heat transmission efficiency decreases, and heat radiation of LEDs cannot be sufficiently performed.
Therefore, sufficient and sure heat radiation measures for light-emitting devices are desired in lighting apparatuses of this type.